President Donald Trump on Tuesday plans to sign an executive order that would bar undocumented immigrants living in the country from being counted in the 2020 census.

It was not immediately clear how undocumented immigrants would be identified in order to omit them from the census count.The census questionnaire, which was distributed in March, did not require respondents to indicate whether they or others in their household are citizens.

The administration attempted last year to add a citizenship question on the 2020 census for the first time in 60 years, but the Supreme Court blocked the Department of Commerce, which oversees the census. In that decision, Chief Justice John Roberts joined the four-member liberal wing of the court and said the administrations rationale for adding it was contrived.

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The census results are used to determine the number of seats in the House of Representatives each state is allocated and impacts the dispersal of billions of federal dollars. Omitting undocumented immigrants has been criticized as an effort to reduce aid to states with large immigrant populations and to reduce the political clout of those areas, which are heavily represented by Democrats.

Trump’s order is likely to prompt legal challenges from Democratic-controlled states that brought the previous lawsuit challenging the citizenship question as unconstitutional. In that case, the opponents argued that a citizenship question would discourage all immigrants from responding and jeopardize the constitutionally-mandated count.

The Constitution directs Congress to conduct a census count of “persons living in the U.S., and does not distinguish between citizens and non-citizens. The Supreme Court has not directly ruled on whether “persons” includes immigrants, but lower courts have said undocumented immigrants should be counted.

“The resident population counts include all people (citizens and non-citizens) who are living in the United States at the time of the census, according to the Census Bureau’s website. People are counted at their usual residence, which is the place where they live and sleep most of the time.”

Trump railed against the Supreme Court decision, but the bureau printed and mailed questionnaires with only the standard questions about race, age, sex, and household size. However, soon after the court defeat last year, the administration was viewed as attempting to circumvent the decision and began asking states for drivers’ license records that often include citizenship data, according to the Associated Press.

While the census count began in March, since the COVID-19 outbreak the timeline for completion has been delayed and updated and a final count is now expected to be delivered the presidents and states next year. People could respond to the census online for the first time this year.

This week, the census bureau began sending staff to households that have not responded. The bureau reported as of July 16th, 62 percent of U.S. households had completed their census form.